Film frame location device comprising means for detecting both leading and trailing edges of frame

ABSTRACT

Frames in a filmstrip are separated by frame lines. The frames are centered relative to further processing means by use of first and second photoelectric measuring means, which determine, respectively, the trailing edge of a preceding frame line and the leading edge of the successive frame line. The frame is centered corresponding to the first determined edge.

United States Patent Inventor Rudolf Paulus Munich, Germany Appl. No.861,775 Filed Sept. 29, 1969 Patented Oct. 19, 1971 AssigneeAGFA-Gevaert Aktiengesellschaft Leverkusen, Germany Priority Sept. 27,1968 Germany P 17 97 439.9

FILM FRAME LOCATION DEVICE COMPRISING MEANS FOR DETECTING BOTH LEADINGAND 50 FieldofSearch ..'.II.:.. 250 219F, 214P,2l9lD;83/5O [5 6]References Cited UNITED STATES PATENTS 3,469,105 9/1969 Stasey 250/219FR3,469,480 9/1969 Nassensteinetal. 250/219FR Primary Examiner Archie R.Borchelt Assistant ExaminerT. N. Grigsby AttorneyMichael S StrikerABSTRACT: Frames in a filmstrip are separated by frame g lines. Theframes are centered relative to further processing rawmg means by use offirst and second photoelectric measuring US. Cl 250/219, means, whichdetermine, respectively, the trailing edge of a 250/214 preceding frameline and the leading edge of the successive Int. Cl G01n 21/30, frameline. The frame is centered corresponding to the first HOlj 39/12determined edge.

Inn. 74 21 4 j n COUNTER FLlPFLOr F 7 uHFLlFlER a 73 75 PERFORATOR 7 l77 78 3; 70a RELAY J 3 [Z I0 were o PAIENTEflum 19 Ian SHEET 1. OF 3 Nan a q 2 Q Q m v. I v .I o m W .w. fix? W Q8 H m c v 9 L a A 5 5m n g m"Q m moGmEmE 9 M7 5:524 A Sula A 55:8 4 n y A m5 v x/bw V moimwzwo 51 $82n vf RN E IEIEI IN V EN TOR. RUDOLF PAULUS Mm! n my having slots whichare parallel to the frame lines. These frame lines are defined as thoseplaces wherein the film strip has an extreme value of transmissivity.One such system is known and described in US. Pat. No. 3,469,480. Eachframe is bound by the trailing edge of the preceding frame line and theleading edge of the successive frame line. Thus in the case of negativesthe frame lines correspond to the maximum value of transmissivity asdetermined by photoelectric means and the trailing edge of the frameline may be located at the first place wherein the transmissivity valuehas decreased by a predetermined amount following such a maximum value.All this is stated in the above-identified US. patent.

However, in this US. patent, only one set of measuring means formeasuring the transmissivity is provided. These measuring means are usedto determine the trailing edge of the preceding frame line and centerthe frame in accordance with this criterion. Thus the first decrease intransmissivity following a maximum value is considered the criterion forcentering the frame. It is assumed that this maximum value oftransmissivity will appear only once in a lengthwise portion of a filmcorresponding to the width of a frame. In order to recognize thetrailing edge of this frame line to center the frame, it is assumed thatat lest in reasonably properly exposed negatives the transmissivity isdecreased by at least a minimum value, for example 3 percent as relatedto the transmissivity existing within the frame line. This assumption isvalid in the majority of cases. However, the possibility exists thatthis criterion is not met at a particular frame line when the exposureof the picture has taken place towards an extremely bright light source,as for example when the picture has been taken through a window into thesunlight or by means of a flash in a dark room which has high lightabsorbing characteristics. In this case the arrangement in accordancewith the above-identified patent cannot result in a proper location ofthe frame by means of locating of the trailing edge of the precedingframe line.

SUMMARY OF THE INVENTION It is an object of this invention to improvethe system set forth in the above-identified patent in such a mannerthat even those frames whose preceding trailing edge does not exhibit asufficient contrast relative to the associated frame line may beproperly centered, without requiring an excess of equipment.

This invention thus comprises an arrangement for determining thelocation of a frame in a filmstrip having a plurality of framesseparated by frame lines each of which has a leading and a trailing edgeso that each frame is bounded by the trailing edge of the precedingframe line and the leading edge of the successive frame line. Itcomprises first measuring means for determining for any frame thelocation of the trailing edge of the preceding frame line and generatinga trailing edge signal signifying said location. It further comprisessecond measuring means for determining for said frame the location ofthe leading edge of the successive frame line, and generating a leadingedge signal signifying said location. Further provided are selectormeans associated with said measuring means for indicating the locationof one of said edges.

Thus in accordance with the present invention, a particular frame may becentered as long as a sufficient transmissivity difference exists etherat the trailing edge of the preceding frame line or the leading edge ofthe successive frame line. This difference may, for example, be 3percent. If, however, the required difference in transmissivity does notexist at either of the edges of the frame lines determining a frame,then the leading edge of the successive frame line is considered thatlocation at which there is an increase in transmissivity by the factorof 1.03 to the maximum value. This means tat the total picture contentof the frame is reproduced in the copy, although the reproduction istranslated relative to the negative by the width corresponding to thetotally underexposed edge. This generally results in satisfactorycopies.

The use of second measuring means requires not only the use of a secondphotoelectric apparatus, but also associated computing equipment toevaluate the signals generated by the photoelectric means. Thesecomputing means are of the digital computer type in the patent mentionedabove. This results in high accuracy but requires a great deal ofequipment. Thus doubling of such equipment for use with the secondphotoelectric means would be impossible for practical purposes. Thus inaccordance with the present invention the photoelectric means arequipped with analog computers containing operational amplifiers. Theoperational amplifiers serve to store a voltages on a condenser whichcorresponds to a measured value of transmissivity. The storedtransmissivity value is then compared by the operational amplifier tothe next subsequent measured transmissivity signal. If the subsequentmeasured transmissivity signal exceeds the stored signal, the highervalue is stored and a counter is reset. -As the measurement progresses,the counter is fed pulses corresponding to the advancement of the filmpast the measuring location. Overflow of the counter serves to activatefurther processing means.

The operational amplifiers and counters are almost identical for boththe first and second photoelectric means. They may be constructed fromintegrated circuits at a fraction of the cost required by thecorresponding digital circuits. The accuracy of the analog computers areentirely sufficient for the particular application.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic diagram forlocating a frame by means of first measurement means employingoperational amplifiers;

FIG. 2 shows an example of the variation of transmissivity along thelength of a film strip;

FIG. 3 shows arrangement of first and second photoelectric meansrelative to the frame lines and relative to further processing means;and

FIG. 4 is a block diagram showing a system using first and secondmeasuring means for locating the frame.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred embodiment of thisinvention will now be discussed with reference to the Figures.

In FIG. 1, the light emanating from a lamp 2 is transmitted through thefilm strip 3 whence it passes through a slot in a diaphragm l. Aphotoelectric receiver 4 thus receives light in the form of a narrowline. The photoelectric receiver 4 may for example be a secondaryelectron multiplier or a photodiode. The output of the photoelectricreceiver 4 is connected to the first input of an operational amplifier 5which serves to compare the signals appearing at its two inputs. If thesignals are unequal in a predetermined direction no output signal isgenerated by the operational amplifier. If, however, both signals areequal or the signal at the first input exceeds that at the second input,then a signal is generated at the output of operational amplifier 5.These signals are herein referred to as possible trailing edge signals.Such operational amplifiers are well known in the field of analogcomputers and may be obtained as a unit in the form of integratedcircuits.

Voltage divider means, here a resistance 6 connected in series to aresistance 7 are connected from the output of photoelectric receiver 4to ground. Resistance 6 is a variable resistor which is smaller thanresistance 7 by a factor of approximately 30. At the common point ofresistors 6 and 7 is connected the first input of a second operationalamplifier 8. The output of this operational amplifier 8 is connected viaa diode 9 to one terminal of a condenser 11 whose other terminal isconnected to ground. Because of the connection via the diode thispermits charging of the capacitor 11 but prevents discharge of saidcapacitor via the operational amplifier. The capacitor serves to providestored transmissivity signals corresponding to the maximum measuredtransmissivity signal as supplied by photoelectric receiver 4. It willbe noted that the diode 9 is connected in parallel to switch contact 10aof a relay It). The first terminal of capacitor lll further connected tothe base of a field effect transistor 12 from whose output a voltagecorresponding to the capacitor voltage may be derived without causingloading of said capacitor and thus a draining of its charge. The voltageon the capacitor is connected to the second input of operationalamplifier 8 and to the second input of operational amplifier 5.Operational amplifier 8 and its associated circuitry may be consideredfirst comparator means, while operational amplifier may be consideredfurther first comparator means. All the above circuitry forms part ofthe first measuring means, as does a counter 13 which is adapted to bereset by the possible trailing edge signals. The counting signals forcounter 13 are supplied by a pulse generator 15 which may for examplegenerate pulses at a frequency of 500 Hz. The pulses are applied to thecounter 13 via an AND-gate M whose second input is supplied by the 1 ofa flip-flop 16, which flip-flop is in turn controlled by the counteroverflow. The 0 output of flip-flop l6 activates an amplifier 17 whichin turn activates further processing means, for example a perforator 18which serves to make a mark at the edge of the film strip. Perforator 18may also serve to activate a switch 19 which is connected in parallel toa starting switch 20. Finally a flip-flop 16, or more particularly its 0output activates relay which closes contact 10a, short-circuiting diode9.

The output of AND-gate 14 also supplies pulses from generator to a stepmotor 2t which advances film strip 3 step by step, each stepcorresponding to 0.2 mm. along the predetermined path past the measuringmeans. Simultaneously the pulses are supplied to the counter 13 which isso arranged that its overflow serves to set flip-flop 16. The capacityof the counter is made substantially equal to the average frame width.

Operation of the above-described arrangement is as follows:

At the beginning, generator 15 oscillates at the determined frequency.However the pulses are not transmitted since AND-gate 14 is blocked byflip-flop 16. If the starting switches now are depressed, flip-flop 16is switched to its set state AND-gate M becomes transmissive, activatingstep motor 21 as well as counter 13. While the film is being advanced,the photoelectric receiver 4 receives light responsive to thetransmissivity of the film strip and generates a current which istransformed into a voltage via voltage divider 6 and '7. The voltagevalue, corresponding to a first comparator signal, is compared with thestored transmissivity signal, namely the signal on capacitor 11, bymeans of the operational amplifier 8. Since, however, contact 10a willclose until the starting switch was depressed, capacitor lll has storedan almost smaller transmissivity according to the foregoing part offilm. Thus the comparison in amplifier 5 generally results in showingthat the measured transmissivity signal is larger than the storedtransmissivity signal. Therefore, the counter 13 is reset.Simultaneously the first comparator signal which is less than themeasured transmissivity signal by a factor determined by theadjustmentof resistance 6 is stored in capacitor 11. The capacitor 11 ischarged via operational amplifier s until both inputs of said amplifierhave the same voltage. Because of re sistance 6 the measuredtransmissivity signal may be less than the stored transmissivity signalby a factor determined by resistance 6, without impeding the generationof possible trailing edge signals by operational amplifier 5. Thus,counter 13 will continue to be reset even though the measuredtransmissivity signals vary somewhat within the frame line due, forexample, to uneven distribution of grain within said frame line. Thefactor of 3 percent may be considered the positioning criterion. As longas the counter is reset it cannot overflow and, as described above, thecounter overflow constitutes the trailing edge signal which activatesthe further processing means.

Thus if a maximum transmissivity value has been determined for afilmstrip of negatives after a number of steps corresponding to a framewidth, it may be assumed with a high degree of certainty that the frameline between two frames is being scanned. However, within the frame linethe counter 10 will continue to be reset, since, as explained above,amplifier 5 will continue to generate possible trailing edge signals.When, however, the actual trailing edge of the frame line is reached,that is when the edge of the picture is opposite the scanning slot, theexposure of the film increases at least as much as the above-mentionedcriterion, causing the transmissivity to decrease correspondingly andthus the comparison at operational amplifier 5 to be decided in favor ofthe stored transmissivity signal. Starting with this point the counter10 is no longer reset since such a high value of transmissivity will notagain be attained until the subsequent frame line. Since the capacity ofthe counter 13 causes it to overflow before this subsequent frame linereaches the position opposite the scanning slot, the counter actuallydoes overflow causing the transport arrangement to come to a standstillbecause of the resetting of flip-flop 16. The resultant 0" output offlip-flop 16 causes the perforator means 18 to be activated viaamplifier l7, and further causes relay 10 to be activated. Relaycontacts 10a then close causing the discharge of capacitor 11, thuscausing the stored transmissivity signal to be extin guished. Theprocessing means 18 which may for example place a mark at the edge ofthe film at a predetermined distance from the located trailing edge ofthe frame line also activates switch 19 momentarily which causesflip-flop 16 to be switched to the set condition. As denoted previously,the flip-flop 16 is thus in the l state which permits transmission ofpulses from pulse generator R5 to step motor 21 and counter 13. Thus anew scanning cycle commences.

While this type of analog operational amplifier for evaluating thesignals furnished by photoelectric receiver 4 does not result in higherreliability of operation, it is to be recommended even for scanning witha single slot, since the equipment required is considerably less thanfor the digital means used in conjunction with the photoelectic means inthe US. patent mentioned above. For further economy, operationalamplifiers 5 and 8 may be contained within a single amplifier unit whichincorporates not only the storing of the maximum transmissivity signal,but also the comparison function which results in the generation of thepossible trailing edge signals.

FIG. 2 shows the variation of transmissivity of the filmstrip when saidfilmstrip is scanned with a slot perpendicular to the lengthwisedirection of said filmstrip, when said slot is narrow compared to thewidth of a frame line. The substantially rectangular maximum values oftransmissivity at the three frame lines are easily recognizable.

In FIG. 3 shown below FIG. 2 the arrangement of the further processingmeans along the length of the filmstrip relative to the first and secondmeasuring means is shown. In this illustration the perforation is to beaffixed to the edge of the filmstrip at a location corresponding to thecenter of the frame. Point 22 shows the location of the trailing edge ofthe last preceding frame line at the time at which the processing means,or perforator, is activated. This trailing edge is denoted by referencenumber 23. The location of the perforator means is denoted by 24 and isas mentioned above, in the center of the located frame. It is removedfrom the previously identified point 22 by scanning steps of 0.2 mm.each, that is by 18 mm. This is exactly half of the average width of 36mm. film.

" A counter 43 is connected to the output of gate counter 13. Counter 43is adapted to be reset by signals At a distance of 176 steps from thestarting point 22, that is 0.8 mm. prior to the end of the average framewidth the first scanning slot 25 issituated which in turn is displacedrelative to'rthe second scanning slot 26 by 184 steps, that is a lengthcorresponding to a full frame width plus the average width of the frameline.

FIG. 4 shows a block diagram of an arrangement using first and secondmeasuring means. 27 and 28 represent respectively. thephotoelectricreceiving means receiving light through slots 25 and 26.Insofar as the components in the arrangement of FIG. 4 corresponds tothose shown in H6. 1 the same reference numbers are used. New componentsare as follows. A further resistance 29 has been added to the voltagedivider comprising resistances 6 and 7. A third operational amplifier 30compares each first measured transmissivity signal with the storedtransmissivity signal derived from capacitor 11. It is the purpose ofoperational amplifier 30 to determine whether, within a distancecorresponding to the width of a frame at least a predetermined minimumnumber of measured transmissivity signals occur which are substantially,for example by percent, smaller than the maximum transmissivity value.

" This requirement is not fulfilled if, for example, the frame istotally unexposed because of failure of the shutter to trip. The signalfurnished by operational amplifier 30, herein called exposure signals,are applied via a gate 31 to'exposure signal counting means, namelycounter 32. Operational amplifier 30 of course constitutes means forfurnishing exposure signals. lf counter 32 has received thepredetermined number of exposure signals, for example 16 signals, aflip-flop 33 is switched. This flip-flop 33 supplies a signal toamplifier l7, herein considered gating means, in such a manner thatamplifier 17 cannot transmit a signal if flip-flop 33 has not switched.Thus pictures which are not suitable for reproduction because ofinsufficient exposure are not marked. Gate 31 is an AND gate at whosesecond input the pulses from pulse generator are applied so that onlypulses which arrive at the correct time may be applied to counter 32.Thus noise pulses cannot be counted.

The measuring means associated with photoelectric receiver 28 aresubstantially equivalent to the arrangement shown in FIG. 1. Operationalamplifier 35 responds to operational amplifier 5, operational amplifier36 with diode 37, capacitor 38 and field effect transistor 39corresponds to the similar component 8, 9, 11 and 12 of HO. 1. However,resistance 6 between the inputs of amplifiers 36 and 35 is missing.These inputs are at equal potential. Instead resistance 7 is dividedinto two resistors 41 and 40. The adjustable resistor'4l which issmaller than resistor 40 by a factor of approximately 30 is shunted by atransistor 42. Transistor 42 works as a switch which is controlled bypulses generated 'by "amplifier 35.

14 as is furnished by operational amplifier 35. The signals are referredto "as possible leading edge signals herein. The outputs of counters 13and 43 are connected to the inputs of an OR-gatc 44 whose output isconnected to a flip-flop 16. OR-gate 44 and flip-flop 16 constituteselector means. The arrangement operates as follows:

The operation of counter 13 with regard to the location of the trailingedge of the preceding frame line has been explained in detail inconnection with FIG. 1.

The operation of the arrangement for locating the leading edge of thesucceeding frame line is as follows.

The signal furnished by photoelectric receiver 28, namely secondmeasured transmissivity signals, are compared to thestoredtransmissivity signals stored in capacitor 38, by amplifi er 35.If, as is to be expected at the beginning of the scanning cycle, thesecond measured transmissivity signal is greater than the storedtransmissivity signal, then amplifier 35 generates a possible leadingedge signal for resetting counter 43. Simultaneously transistor 42 isblocred bythe possible leading edge signal, so that resistance 41becomes effective.

Since photoelectric receiver 28 acts as a constant current source, thesame current flows in the circuit regardless of load resistance, so thatthe voltage appearing at the terminal of resistance 40 connected to theinput amplifier 36 is increased by a factor determined by the ratio ofthe two resistances, tat is, is increased by this amount relative toground potential. This increased value is now stored via amplifier 36 incapacitor 38. After the leading edge signal has disappeared, transistor42 again becomes conductive so that the potential at the input ofamplifiers 35 and 36 returns to the original value. At the next scanningstep the voltage at the inputs of amplifier 35 will then only beconsidered equal, if the next measured value is higher than the storedvalue .by an amount corresponding to the above-mentioned factor. Thismeans that counter 43 is only reset if the transmissivity function has apositive steplike increase corresponding at leastto this factor beforereaching a maximum transmissivity value. The probability that thiscondition is satisfied anywhere except at the leading edge of thesuccessive frame line is, for allpractical purposes, nil.

If the arrangement has thus located the leading edge of the successiveframe line, thenno further second measured transmissivity values willoccur which satisfy the requirements for resetting the counter 43. Thecounter thus advances steadily via the counter signals furnished bypulse generator 15 until it reaches the end of its capacity whichcorresponds approximately to the width of a frame. Since both the firstand second measuring system operates independently of one another thatcounter of counters 13 and 43 will set flip-flop 16 via gate 44 which isthe first to overflow. It is possible of course that both countersoverflow simultaneously if the trailing edge of the preceding frame lineis opposite the first slot at the same time that the leading edge of thesuccessive frame line is opposite the slot associated with the secondmeasuring means.

The perforator means 18 will be activated as described above viaamplifier 17 if the flip-flop 33 has been switched because counter 32has received a sufficient number of exposure signals. Operation of theperforator 18 causes switch 19 to close momentarily, setting flip-flop16. This causes counters 13, 14 and 32 to be reset. This resetting ofthe counters may also be effected by means of a switch 46 whose closurefurnishes a signal to OR-gate 45. This switch may for example beactivated by a marking on the film which indicates a place where twoindividual film strips were joined. A new scanning cycle recommencesafter discharge of capacitors-11 and 38 and when gate 14 again permitsthe transmission of pulses to counters 13 and 43.

The above embodiment with the given numbers is particularly arranged forfilms having a frame length of 36 mm. For pictures of a'size of l8 24mm. or rectangular shape, the distance between point 22 and the scanninglocations of slots "25 and 26, as well as a change in the capacity ofthe counters l3 and 43 must be effected. These changes can of course bereadily accomplished.

The arrangements described above can of course also be used if thefurther processing means are the printer, rather than a perforatingmeans for marking the center of the film. The arrangement can then beused to center the film directly within the printer.

While the invention has been illustrated and described as embodied inparticular types of analog circuits, it is not intended to be limited tothe details shown, since various modifications and structural andcircuit changes may be made without departing in any way from the spiritof the present invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

1. Arrangement for determining the location of a frame in a filmstriphaving a plurality of frames separated by frame lines each of which hasa leading and a trailing edge so that each frame is bounded by thetrailing edge of the preceding frame line and the leading edge of thesuccessive frame line, comprising, in combination, first measuring meansfor determining for any frame the location of the trailing edge of thepreceding 7 frame line and generating a trailing edge signal signifyingsaid location; second measuring means for determining for said frame thelocation of the leading edge of the successive frame line and generatinga leading edge signal signifying said location; and selector meansassociated with said measuring means for indicating the location of oneof said edges.

2. An arrangement as set forth in claim 1, wherein said filmstrip has anextreme value of light transmissivity at said frame lines; wherein saidtrailing edge and said leading edge of said frame lines arecharacterized, respectively, by a predetermined change of transmissivityfrom and to said extreme value; and wherein said first and secondmeasuring means each comprise photoelectric means for measuring saidtransmissivity.

3. An arrangement as set forth in claim 2 further comprising transportmeans for transporting said filmstrip along a predetermined lengthwisepath; and wherein said first and second measuring means are at a firstand second location along said predetermined lengthwise path; andwherein said second location is spaced from said first location by adistance corresponding to the length of a frame.

4. An arrangement as set forth in claim 3, wherein each of saidmeasuring means comprise a light slot parallel to said frame lines.

5. An arrangement as set forth in claim 4, wherein each of said lightslots is narrow compared to the width of one of said frame lines.

6. An arrangement as set forth in claim 4 wherein said selector meansare responsive to the first generated one of said trailing edge andleading edge signals.

7. An arrangement as set forth in claim 3, wherein further processingmeans are located at a determined location along said path; and whereinsaid selector means are adapted to generate a position signal indicatingthe position of said frame relative to said further processing means independence upon said leading or trailing edge signals.

8. An arrangement as set forth in claim 7, wherein said firstmeasurement means comprise means for generating first measuredtransmissivity signals during the transport of said filmstrip past saidfirst location; first comparator means for comparing first comparatorsignals corresponding to said first measurement signals to a storedtransmissivity signal and storing the greater of the two, said storedtransmissivity signal thus corresponding to an extreme value oftransmissivity; said first comparator means being further adapted togenerate a possible trailing edge signal when a measured transmissivitysignal is less than the stored transmissivity signal.

9. An arrangement as set forth in claim 8, wherein said firstmeasurement means further comprise first delay means responsive to saidpossible trailing edge signal and adapted to generate said trailing edgesignal after a predetermined delay corresponding to transport of apredetermined portion of said filmstrip past said first location, saiddelay recommencing in full upon receipt of a subsequent possibletrailing edge signal prior to generation of said trailing edge signal.

10. An arrangement as set forth in claim 9, wherein said firstcomparator means comprise first operational amplifier means having afirst operational amplifier input for receiving said first comparatorsignal, a second operational amplifier input for receiving a feedbacksignal, a first operational amplifier output for furnishing a signalcorresponding to the greater of the signals applied at the first andsecond operation amplifier inputs, a capacitor for storing said greatersignal, and feedback means for connecting the output of said capacitorto said secondoperational amplifier input.

11. An arrangement as set forth in claim 10, further comprising voltagedivider means for furnishing said first comparator signals as apredetermined percentage of said first measurement signals.

12. An arrangement as set forth in claim 11, wherein said further firstcomparator means comprise further operational amplifier means.

13. An arrangement as set forth in claim 9, wherein said transport meanstransport said film in steps; and wherein said delay means comprise acounter connected to the output of said further first comparator meansin such a manner that each possible trailing edge signal resets saidcounter; further comprising pulse-generating means for generating pulsessignifying each transport step; and means for applying said pulses tosaid counter to constitute counting signals, the overflow of saidcounter corresponding to generation of said trailing edge signal.

14. An arrangement as set forth in claim 10, further comprising acapacitor connected to said first operational amplifier output; whereinsaid feedback means comprise an isolating stage for preventing saidsecond amplifier input from loading said capacitor.

15. An arrangement as set forth in claim 14, wherein said isolatingstage comprises a field effect transistor.

16. An arrangement as set forth in claim 13, wherein the capacity ofsaid counter is substantially equal to, but slightly less than, thewidth of a frame.

17. An arrangement as set forth in claim 7, wherein said secondmeasurement means comprise second comparator means for comparing secondcomparator signals corresponding to second measurement signals increasedby a predetermined percentage to stored transmissivity signals andstoring the greater of the two, said stored transmissivity signals thuscorresponding to maximum transmissivity values; and wherein said secondmeasurement means comprises further second comparator means forcomparing second measured transmissivity signals to said storedtransmissivity signals and generating a possible leading edge signalwhen a second measurement signal exceeds the stored transmissivitysignal.

18. An arrangement as set forth in claim 7 wherein said selector meanscomprise an OR circuit having a first input for receiving said trailingedge signal, a second input for receiving said leading edge signal, andan OR output for generating a position signal.

19. An arrangement as set forth in claim 18, wherein further processingmeans are located at a third location along said predetermined path ofsaid filmstrip following said first and second location; and whereinsaid position signal activates said further processing means.

20. An arrangement as set forth in claim 19, further comprising gatingmeans for gating the application of said position signal to said furtherprocessing means in dependence upon the presence of exposure signalsindicating that said frame has been exposed; and means for furnishingsaid exposure signals in dependence upon said first measuredtransmissivity signals.

21. An arrangement as set forth in claim 20, wherein said means forfurnishing exposure signals comprises third operational amplifier meansadapted to compare said first measured transmissivity signals with saidstored transmissivity signals and generate said exposure signals when apredetermined difference exists therebetween; and exposure signalcounting means for counting the number of said exposure signals.

22. An arrangement for determining the location of a frame in afilmstrip having a plurality of frames separated by frame lines each ofwhich has a leading and a trailing edge so that each frame is bounded bythe trailing edge of the preceding frame line and the leading edge ofthe'successive frame line, comprising, in combination, photoelectricmeans for generating measured transmissivity values corresponding to thetransmissivity of said filmstrip; operational amplifier means forcomparing said measured transmissivity signals to stored transmissivitysignals and storing the greater of the two, said operational amplifiermeans being further adapted to generate a possible trailing edge signalwhen a measured transmissivity signal exceeds the stored transmissivitysignal; counter means having a predetermined capacity corresponding tothe width of a frame, sad counting means being further adapted to countcounting signals and to generate a position signal upon overflow; pulsegenerator means for furnishing said counting signals; transport meansfor transporting said film along a said predetermined distancecorresponding to the capacity of said counter; and means for activatingsaid additional processing means in response to said position signal.

1. Arrangement for determining the location of a frame in a filmstriphaving a plurality of frames separated by frame lines each of which hasa leading and a trailing edge so that each frame is bounded by thetrailing edge of the preceding frame line and the leading edge of thesuccessive frame line, comprising, in combination, first measuring meansfor determining for any frame the location of the trailing edge of thepreceding frame line and generating a trailing edge signal signifyingsaid location; second measuring means for determining for said frame thelocation of the leading edge of the successive frame line and generatinga leading edge signal signifying said location; and selector meansassociated with said measuring means for indicating the location of oneof said edges.
 2. An arrangement as set forth in claim 1, wherein saidfilmstrip has an extreme value of light transmissivity at said framelines; wherein said trailing edge and said leading edge of said framelines are characterized, respectively, by a predetermined change oftransmissivity from and to said extreme value; and wherein said firstand second measuring means each comprise photoelectric means formeasuring said transmissivity.
 3. An arrangement as set forth in claim 2further comprising transport means for transporting said filmstrip alonga predetermined lengthwise path; and wherein said first and secondmeasuring means are at a first and second location along saidpredetermined lengthwise path; and wherein said second location isspaced from said first location by a distance corresponding to thelength of a frame.
 4. An arrangement as set forth in claim 3, whereineach of said measuring means comprise a light slot parallel to saidframe lines.
 5. An arrangement as set forth in claim 4, wherein each ofsaid light slots is narrow compared to the width of one of said framelines.
 6. An arrangement as set forth in claim 4 wherein said selectormeans are responsive to the first generated one of said trailing edgeand leading edge signals.
 7. An arrangement as set forth in claim 3,wherein further processing means are located at a determined locationalong said path; and wherein said selector means are adapted to generatea position signal indicating the position of said frame relative to saidfurther processing means in dependence upon said leading or trailingedge signals.
 8. An arrangement as set forth in claim 7, wherein saidfirst measurement means comprise means for generating first measuredtransmissivity signals during the transport of said filmstrip past saidfirst location; first comparator means for comparing first comparatorsignals corresponding to said first measurement signals to a storedtransmissivity signal and storing the greater of the two, said storedtransmissivity signal thus corresponding to an extreme value oftransmissivity; said first comparator means being further adapted togenerate a possible trailing edge signal when a measured transmissivitysignal is less than the stored transmissivity signal.
 9. An arrangementas set forth in claim 8, wherein said first measurement means furthercomprise first delay means responsive to said possible trailing edgesignal and adapted to generate said trailing edge signal after apredetermined delay corresponding to transport of a predeterminedportion of said filmstrip past said first location, said delayrecommencing in full upon receipt of a subsequent possible trailing edgesignal prior to generation of said trailing edge signal.
 10. Anarrangement as set forth in claim 9, wherein said first comparator meanscomprise first operational amplifier means having a first operationalamplifier input for receiving said first comparator signal, a secondoperational amplifier input for receiving a feedback signal, a firstoperational amplifier output for furnishing a signal corresponding tothe greater of the signals applied at the first and second operationamplifier inputs, a capacitor for storing said greater signal, andfeedback means for connecting the output of said capacitor to saidsecond operational amplifier input.
 11. An arrangement as set forth inclaim 10, further comprising voltage divider means for furnishing saidfirst comparator signals as a predetermined percentage of said firstmeasurement signals.
 12. An arrangement as set forth in claim 11,wherein said further first comparator means comprise further operationalamplifier means.
 13. An arrangement as set forth in claim 9, whereinsaid transport means transport said film in steps; and wherein saiddelay means comprise a counter connected to the output of said furtherfirst comparator means in such a manner that each possible trailing edgesignal resets said counter; further comprising pulse-generating meansfor generating pulses signifying each transport step; and means forapplying said pulses to said counter to constitute counting signals, theoverflow of said counter corresponding to generation of said trailingedge signal.
 14. An arrangement as set forth in claim 10, furthercomprising a capacitor connected to said first operational amplifieroutput; wherein said feedback means comprise an isolating stage forpreventing said second amplifier input from loading said capacitor. 15.An arrangement as set forth in claim 14, wherein said isolating stagecomprises a field effect transistor.
 16. An arrangement as set forth inclaim 13, wherein the capacity of said counter is substantially equalto, but slightly less than, the width of a frame.
 17. An arrangement asset forth in claim 7, wherein said second measurement means comprisesecond comparator means for comparing second comparator signalscorresponding to second measurement signals increased by a predeterminedpercentage to sTored transmissivity signals and storing the greater ofthe two, said stored transmissivity signals thus corresponding tomaximum transmissivity values; and wherein said second measurement meanscomprises further second comparator means for comparing second measuredtransmissivity signals to said stored transmissivity signals andgenerating a possible leading edge signal when a second measurementsignal exceeds the stored transmissivity signal.
 18. An arrangement asset forth in claim 7 wherein said selector means comprise an OR circuithaving a first input for receiving said trailing edge signal, a secondinput for receiving said leading edge signal, and an OR output forgenerating a position signal.
 19. An arrangement as set forth in claim18, wherein further processing means are located at a third locationalong said predetermined path of said filmstrip following said first andsecond location; and wherein said position signal activates said furtherprocessing means.
 20. An arrangement as set forth in claim 19, furthercomprising gating means for gating the application of said positionsignal to said further processing means in dependence upon the presenceof exposure signals indicating that said frame has been exposed; andmeans for furnishing said exposure signals in dependence upon said firstmeasured transmissivity signals.
 21. An arrangement as set forth inclaim 20, wherein said means for furnishing exposure signals comprisesthird operational amplifier means adapted to compare said first measuredtransmissivity signals with said stored transmissivity signals andgenerate said exposure signals when a predetermined difference existstherebetween; and exposure signal counting means for counting the numberof said exposure signals.
 22. An arrangement for determining thelocation of a frame in a filmstrip having a plurality of framesseparated by frame lines each of which has a leading and a trailing edgeso that each frame is bounded by the trailing edge of the precedingframe line and the leading edge of the successive frame line,comprising, in combination, photoelectric means for generating measuredtransmissivity values corresponding to the transmissivity of saidfilmstrip; operational amplifier means for comparing said measuredtransmissivity signals to stored transmissivity signals and storing thegreater of the two, said operational amplifier means being furtheradapted to generate a possible trailing edge signal when a measuredtransmissivity signal exceeds the stored transmissivity signal; countermeans having a predetermined capacity corresponding to the width of aframe, sad counting means being further adapted to count countingsignals and to generate a position signal upon overflow; pulse generatormeans for furnishing said counting signals; transport means fortransporting said film along a predetermined path and adapted to beactivated by said pulses from said pulse generator means; additionalprocessing means located a predetermined distance from said measuringmeans, said predetermined distance corresponding to the capacity of saidcounter; and means for activating said additional processing means inresponse to said position signal.